Field of the Invention
Embodiments of the current invention relate to methods and systems to detect, classify, and mitigate impulsive noise.
Description of the Related Art
Telecommunications companies are providing subscribers an increasing number of services, such as voice, video, data, high definition television (HDTV), and interactive gaming. In some instances, these services may be offered over existing telephone lines that provide plain old telephone service (POTS). The lines may include cables that run from the service provider's central office or exchange to the subscriber's premises. Each cable may include up to one hundred copper twisted pair wires, wherein the twisted pairs may be unshielded (UTP) or shielded (STP) and each wire may be 24 or 26 gauge. One or more UTPs may connect to each subscriber's house.
The services may be provided using digital subscriber line or digital subscriber loop (DSL) type protocols, such as asymmetric DSL (ADSL), high data rate DSL (HDSL), integrated services digital network (ISDN) DSL (IDSL), rate adaptive DSL (RADSL), symmetric DSL (SDSL), symmetric high speed DSL (SHDSL), very high speed DSL (VDSL), and the like. The bandwidth associated with these protocols may be up to 30 megahertz (MHz), which supplies downstream data rates to the subscriber ranging from 1.5 megabits per second (Mbps) in the case of ADSL to 150 Mbps in the case of VDSL or VDSL2. The loop distances for these protocols may range from about 3.7 kilometers for lower data rate protocols to about 300 meters for higher data rate protocols.
Signals providing the services from the telecommunications company may be received by a modem in the subscriber's household. The modem typically receives power from a household power line. The signals, supplied at high data rates over unshielded wires, are susceptible to noise interference which degrades the performance of the DSL services. Sources of noise may include crosstalk from other DSL signals, radio ingress of AM or amateur radio stations, thermal noises in the line or receiver analog components, electromagnetic couplings of signals from twisted pair wires (used for household power line) associated with the DSL, various appliances at the home (such as hair dryers, vacuum cleaners, light switches, nearby computers, and garage door openers), electrical power supply units for laptop or desktop computers, routers, televisions and other entertainment electronics, internal power and telecommunication cables that run close together, and the like. The noise from these sources can be time variable, relatively stationary, impulsive, or combinations thereof.
Impulsive noise may be a bursty noise event, typically of electromagnetic origin, with potentially high amplitude in voltage, current, or power but limited in duration. Impulsive noise is inherently difficult to characterize and filter out without impacting the characteristics and quality of the underlying signals, but may be characterized statistically through its amplitudes, duration, inter-arrival times, and frequency spectrum. Proper characterization of impulsive noise is important to help identify and possibly eliminate the source of the noise.